1. Field of the Invention
The present invention relates to a rolling bearing including a synthetic-resin cage.
2. Description of Related Art
As a synthetic-resin cage that holds rolling elements arranged between an inner ring and an outer ring of a rolling bearing, a so-called half-encasing cage is known. The half-encasing cage has a plurality of pockets formed at regular intervals to hold balls. Each of the pockets is shaped to be open toward one side in an axial direction so as to allow the ball to be installed in the pocket. When a rolling bearing with the half-encasing cage rotates at high speed, a resultant centrifugal force causes a portion of the cage on one side in the axial direction, that is, the side to which the pockets open, to be deformed and opened. As a result, the cage and the balls interfere with one another so that a rotary torque of the rolling bearing may increase or seizure may occur in the rolling bearing.
On the other hand, a fully-encasing synthetic-resin cage is also known which can be used even under a high-speed rotation condition (see, for example, Japanese Patent No. 4946881). The resin cage is constructed by coupling a pair of split members formed like rings. The split members have the identical shape and each have a plurality of pocket portions and a plurality of coupling portions alternately arranged in a circumferential direction. Each of the pocket portions has a shape resulting from splitting of a pocket in two halves. The coupling portions of each of the split members are coupled to the coupling portions of the other split member. Each of the coupling portions of the split member has an engagement pawl and an engagement groove formed adjacently to each other in the circumferential direction. The engagement pawls on one of the split members are inserted into and engaged with the corresponding engagement grooves in the other split member. Consequently, the coupling portions of the split members are coupled together so as to be inseparable in the axial direction.
However, in the resin cage described in Japanese Patent No. 4946881, the engagement pawl and the engagement groove need to be formed on each of the coupling portions of the split member. Thus, a mold used to mold the cage has a complicated structure. As a result, production costs for the mold is disadvantageously expensive. The engagement pawl has a base portion and a pawl portion. The base portion protrudes in the axial direction. The pawl portion protrudes from a tip portion of the base portion in a radial direction. Molding the engagement pawl having two portions (the base portion and the pawl portion) with different protruding directions needs not only a mold that is detached in the axial direction but also a mold that is detached in the radial direction. Consequently, the mold has a complicated structure.
On the other hand, the resin cage described in Japanese Patent No. 4946881, the coupled split members may be misaligned with each other in the radial direction, for example, due to a variation in molding of the engagement pawls.